1. Field of the Invention
The present invention relates to the characterization of blood and other bodily fluids, and, more particularly, to the spectrophotometric characterization of blood types and other substances in the blood.
2. Description of Related Art
Current technology for blood typing or for the diagnosis of pathogens requires analysis by microscopy and/or immunoassay techniques. Specifically, for blood typing, an agglutination reaction is used that results from the association of specific antibodies with antigens present on the erythrocyte (red blood cell) surface. The disadvantages of this procedure are that they require significant amounts of time, trained individuals, and well-equipped laboratory facilities. For blood typing, for instance, an involved laboratory procedure is needed to detect the cell surface antigens.
Another limitation of the currently employed technology is a lack of on-line capability for the characterization of particles in bodily fluids, as well as a lack of portable instrumentation capable of detecting, counting, and classifying specific microorganisms, cells, and/or viruses of interest. The problem of portable instrumentation and suitable methods of analysis and diagnosis is particularly relevant to the medical industry, where the need for rapid analysis and diagnosis often involves life-threatening situations. Many times the need for portable instrumentation is further accentuated by the remoteness of the areas where epidemics often occur. Although the analytical instrumentation used in medical and clinical laboratories has improved considerably over the past decade, there are still no suitable techniques capable of detecting, classifying, and counting on-line critical cell populations and/or pathogens in bodily fluids. Typically the microorganisms and viruses of interest have sizes ranging between 0.5 and 20 .mu.m, and, in many instances, are present in fairly dilute concentrations.
As is known from spectroscopy theory, a measure of the absorption of a solution is the extinction coefficient, which also provides a measure of the turbidity. Spectra in the visible region of the electromagnetic spectrum reflect the presence of metal ions and large conjugated aromatic structures double-bond systems. In the near-uv region small conjugated ring systems affect absorption properties. However, suspensions of very large particles are powerful scatterers of radiation, and in the case of microorganisms, the light scattering effect is sufficiently strong to obliterate absorption effects. It is therefore known to use uv/vis spectroscopy to monitor purity, concentration, and reaction rates of such large molecules.
Many attempts have been made to estimate the PSD and the chemical composition of suspended particles using optical spectral extinction (turbidity) measurements. However, previously used techniques require that either the form of the PSD be known a priori or that the shape of the PSD be assumed. The present inventor has applied standard regularization techniques to the solution of the turbidity equation and has demonstrated correct PSDs of a large variety of polymer lattices, protein aggregates, silicon dioxide particles, and microorganisms.